Screen clearers for grain cleaning apparatus



Nov. 1 1966 R. D. MITCHELL 3,282,424

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\ SCREEN CLEARERS FOR GRAIN CLEANING APPARATUS 5 Sheets-Sheet 4 OriginalFiled Nov. 22, 1961 INVENTOR. R0551 D. MITCHELL ATTOENEYS.

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SCREEN CLEARERS FOR GRAIN CLEANING APPARATUS Original Filed Nov. 22,1961 5 Sheets-Sheet 5 WE IZZ i u n h': i

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United States Patent 3,282,424 SCREEN CLEARERS FORGRAIN CLEANINGAPPARATUS Robert D. Mitchell, Buffalo, N.Y., assignor to S. Howes Co.,Inc., Silver Creek, N.Y. Original application Nov. 22, 1961, Ser. No.154,245. Divided and this application Apr. 29, 1965, Ser. No.

. 2 Claims. cr 209-3ss This application is a division of my co-pendingapplication, Serial No. 154,245 filed November 11,- 1961, now abandoned.

This invention relates to apparatus for cleaning dry granular materialby removing therefrom various undesirable material. For instance, theapparatus may be usefully employed in cleaning, cereal grain byseparating therefrom dust, chaff, seeds, undersize grain, dirt, andother foreign matter.

The appartus of the present invention, speaking generally, employesseveral superposed vibratory classifying screens in conjunction with aircurrents for carrying off chaff and other light undesired particles andmaterial. The use of this general arrangement for cleaning grain is wellknown and the present invention is directed, among other things, to animproved general arrangement and cooperation of several of thefunctional components of grain cleaning apparatus of the general typeindicated above.

While this application discloses and discusses the improvements of thepresent invention particularly with reference to cleaning apparatus forcereal grain, certain of the novel principles and teachings of theinvention are applicable to apparatus for grading and separating otherdry granular material according to different types and sizes .and arealso applied to combined apparatus for both grading and cleaning thegrain or other dry granular material.

Due to the employment of vibratory screens for separating good cleangrain from various undesirable materials, which screens are caused toreciprocate rapidly in a generally longitudinal direction, highlyundesirable but generally unavoidable vibration of the entire machinestructure is a commonplace. The means for vibrating the screens reactsagainst the machine framework and thus vibrates the entire grain cleanerstructure to a very marked degree. The reactionary vibration of themachine frame appears to manifest itself as an oscillatory movementabout a generally horizontal transverse axis.

It is conventional in the prior art in apparatus of this general type toprovide reciprocating brushes beneath the screen to keep the screensclear and unclogged. The present apparatus provides novel fluid pressureactuated brush drive means 'which avoids the usual necessity formechanical driving connections between the brush elements and thegeneral framework of the machine.

The low pressure pneumatic power system for reciproeating the brushes isalso superior to the positive mechanical drive means employed in theprior art for the reason that overloading or blockage of the screensthat prevents the reciprocation of the brushes will not cause mechanicalbreakdown owing to the yieldability of thedrive. The compressible fluiddrive medium permits the brushes to stop without damage and startagainst when the obstacle is cleared.

- Other objects and advantages of the grain cleaner apparatus of thepresent invention will become apparent to those skilled in this art fromastudy of the exemplary form hereinafter set forth. However, while aparticular embodiment is illustrated in the accompanying drawings and isdescribed in detail in the following specification, it is to beunderstood that such embodiment is by way of example only and that theprinciples of the invention may be variously applied and employed. Thespirit and scope of the invention is not to be considered as limited tothe form set forth herein by way of example nor otherwise than asdefined in the appended claims.

In the drawings:

FIG. 1 is a general side elevational view of one form of the graincleaner apparatus of the present invention;

FIG. 2 is an end elevational view of theapparatus of FIG. 1 viewed fromthe right hand end of FIG. 1;

FIG. 3 is a schematic view taken similarly to FIG. 1 showing the airflow passages and other portions of the apparatus diagrammatically;

FIG. 4 is a fragmentary top plan view of a portion of the screen andscreen housing structure of the apparatus of FIGS. 1 and 2, partly incross-section; and

FIG. 5 is a fragmentary cross-sectional view taken generally asindicated by the line V-V of FIG. 1 but on a larger scale.

Like characters of reference denote like parts throughout the severalfigures of the drawings. In the exemplary embodiment of the inventionset forth herein to illustrate the various novel principles and featuresof the invention a rigid framework of horizontal and vertical structuralmembers designated generally by the numeral 20 supports the variousoperating components of the machine in their proper relative positions.

In general the upper portion of the machine includes a feed box or entry.arrangement for the grain to be cleaned and a blower or fan withappropriate duct work for connecting the suction side thereof to take uprelatively light undesired matter from the grain being cleaned. Thisupper portion is shown schematically in FIG. 3. The lower portion of themachine is given over principally to a so-called screen deck whichcomprises a series of slightly inclined superposed vibratory orreciprocatoryscreens with brush means for maintaining the screens clearand effective to accomplish their screening functions. The screendeckstructure and the brushing mechanism are illustrated mainly in FIGS.4 and 5.

Mounted generally centrally of the upper portion 0 "the machine is acentrifugal fan or blower designated generally by the numeral 21 andhaving its axis of rota tion extending lengthwise of the machine, thatis, from the feed end to the delivery end. Blower 21 has two axial inletports designated 22 and 23 which are directed. respectively, toward thehead orfeed end of the machine and toward the tail or delivery end.

Blower 21 discharges laterally, as at 24, air which in normal operationhas picked up and subsequently discharged chaff, light dirt andv dustand other foreign matter which it draws from the grain. and isseparated'from in a manner which will presently appear. The rotor shaftof fan or blower 21 is shown at 25 in FIG. 2.

As will be noted from a consideration of FIGS. 1 and 3, blower inletport 22 communicates with a head chamber 26 and blower inlet port 23communicates with a tail chamber 27. Mounted alongside of the headchamber 26 at the extreme right hand side of the machine as viewed inFIG. 1 is a feed box 30 into which the grain to be cleaned is deposited.

As schematically indicated in FIG. 3 the hoods which form the head andtail chambers 26 and 27 are separable from the underlying duct structuregenerally along a horizontal plane through the axis of blower rotorshaft 25. Thus removal of the head and tail chamber hoods exposes theair passage duct portions for ready access for cleaning or otherpurposes.

Referring to the schematic view, FIG. 3, a desired flow of grain fromfeed box 30 passes into the lower portion of a vertical duct or suctionleg 31 which leads upwardly to the head chamber 26, the grain droppingto the head end of a screen deck or housing shown generally in FIGS. 1and 3.

The feed box and the means for controlling the rate of grain feedtherefrom are best shown in FIG. 3 wherein the numeral 32 designates anentry or filler duct and the numerals 33 and 34 designate a pair ofinclined wall members which converge downwardly to form a restrictedgrain passageway.

A helical screw conveyor distributor member 35 is disposed in the apexformed by the wall members 33 and 34 and the helical formations thereofare of opposite hand in both directions outwardly from the center of thescrew membed toward its ends. Accordingly, grain flowing downwardly tothe screw member 35 is distributed outwardly toward the opposite ends ofthe trough formed by the wall members 33 and 34 so that the grain ismore or less uniformly distributed along the feed box 30 which iselongated in a direction perpendicular to FIG. 3.

From the aforesaid trough the grain falls to a further pair of inclinedtrough-forming wall members 37 and 38, the former of which is fixedwithin the feed box 30 and the latter of which is attached to severalarms 39 which are fixed to an adjusting rock-shaft 40 mounted inbearings at the outside of feed box 30. A feed wheel 41 is mounted inthe trough formed by the wall members 37 and 38 and is provided withvanes which extend therealong in an axial direction whereby grain is feddownwardly through the trough by rotation of feed wheel 41.

Means are provided for regulating the rate of feed of the grainindependently of the speed of rotation of the feed wheel 41 by movingthe adjacent portion of the wall member 38 toward and away from feedwheel 41 to reduce or enlarge the passageway. It will be noted from FIG.3 that rockshaft 40 is provided with control arms 44 which terminate incam followers 45 which engage adjustable control cams 46. Extension coilsprings 47 hold followers 45 in engagement with cams 46.

The springs 47 also provide a yieldable means for urging the movablewall member 38 toward the fixed wall member 37. Thus when unusuallylarge pieces of ma terial must pass between these wall members the Wallmember 38 may move resiliently away from wall member 37 to permit suchpassage, by rotation of feed Wheel 41, without damage to the plates orassociated mechanism. After the large piece has passed between the wallmembers the spring 47 will return wall member 38 to its adjustedposition.

Cams 46 are fixed to a camshaft 48 and a handwheel 50, shown in FIG. 1,regulates the angular positions of earns 46 by way of a worm and wheelconnection with camshaft 49 as at 51. The distributing screw member 35and the feed wheel 41 are belt connected as shown at 53 in FIG. 2 forrotation in the same "direction at approximately the same speed, thescrew member 35 being driven from feed wheel 41 as will later appear.

As shown in FIG. 2, an electric driving motor mounted on the top offramework 20 is belt connected as at 61 to the rotor shaft 25 of blower21 to drive the same. A further belt connection 59 from shaft 25 extendsto a speed reducing gear unit 62 having an output shaft 63 and feedwheel 41 is belt connected to the latter as indicated at 64 in FIGS. 1and 2.

numeral 65 in FIG. 1 and further details of which are shown moreparticularly in FIGS. 4 and 5.

Referring to FIG. 1, the screen deck structure comprises generally ahousing having side walls 66 and top and bottom walls 67 and 68. Theside walls 66 extend generally longitudinally and in a downwardlyinclining direc tion toward the tail end of the machine, the left handend as viewed in FIG: 1. At the right hand end the housing 'is enlargedupwardly as clearly shown at 69 in FIG. 1,

thus forming a receiving chute for material falling from 1 the feed box30.

bers.

The screen housing is suspended for reciprocatory movement in agenerally left-to-right horizontal direction as viewed in FIG. 1 bypairs of fore and aft flexible steel straps designated '70 and 71,respectively, which straps are attached to the machine framework attheir upper ends and to the screen housing structure at their lowerends. The screen housing structure is adapted to be rapidly reciprocatedfor effective vibratory screening action by a conventional eccentricdrive mechanism designated 73 in FIG. 1. A typical drive of this type,known in the art as a Buhler drive, is shown in Roth Patent No.1,517,587.

In the present instance the eccentric drive mechanism 73 is driven froma countershaft 75 by a belt connection 76 and the countershaft 75 isdriven from the output shaft 63 of speed reducer 62 by a belt connection77.

Supported between the side walls 66 of the screen housing structure area series of three superposed screens including a relatively shortscalper screen 80, shown in dot and dash linesin FIG. 3, which ispositioned in the up wardly extending right hand portion 69 of thescreen housing and inclines downwardly to the right as viewed in FIGS. 1and 3. The remaining two screens, one above the other, are designated 81and 82 and inclined downwardly to the left as viewed in FIG. 1. Theupper screen 81 is generally called the main screen and the lower screen82 is called the sand or seed screen. Each of these screens in thepresent instance comprises two screen units in edge to edge relation, aswill later appear.

The scalper screen 80 receives the grain falling from the feed box 30 byway of the suction leg 31 and since the scalper screen is of relativelycoarse mesh it passes all excepting the larger pieces of foreign matteror debris, the latter being discharged from the machine by way of achute designated in FIG. 1.

The main screen 81 is of such mesh as to pass good grain but holdthereon all undesired matter larger than the good grain. The lowermostscreen 82 which finally receives the grain through the main screen is ofrelatively fine mesh and merely passes sand, seeds and similar fineimpurities which are generally of smaller particle size than the goodclean grain. Foreign matter held on main screen 81 discharges through achute 83 and fines falling through screen 82 to bottom pan or Wall 68pass out of the machine through a duct 84.

The screen deck structure is the subject of further novelty as to themeans and method of mounting and releasably securing the screen elementstherein and as to the means provided for brushing the bottoms of thescreens to maintain the same clear and unclogged for performing theirscreening functions. Further details of the screen structure will bedescribed later herein, following a description and discussion of thegeneral structure and operation of the grain cleaner generally. Inthis-connection reference will now be had to the diagrammatic view, FIG.3, which presents the grain cleaner as viewed in FIG. 1 but in schematicform.

The feed box 30 and its adjuncts and the suction leg 31 adjacent theretohave been previously described, as has the blower 21 and its two inletports 22 and 23 and its discharge duct 24. It will be noted from FIG. 3that good grain from the lower end of the final screen 82 dischargesinto the lower end of a vertical duct 85 called herein the tail airsuction leg. It will be noted also that the head and tail suction legs31 and 85 discharge at their upper ends into the head and tail chambers26 and 27, respectively.

'To promote precipitation of chaff and other light materials from theair passing from the suction legs 31 and 85 through the head and tailchambers 26 and 27 and to the blower 21 thehead and tail chambers areeach provided with a series of bafiles which cause the air to pursue atortuous expanding path through the head and tail cham- This expansionof the area of the flow path in the direction of flow reduces thevelocity of the air whereby solid particles entrained therein fall intohoppers 86 and 87 at the lower ends of these chambers, from'whence it ismoved laterally from the machine by means of a pair of conveyor screws88 and 89, respectively.

Referring to the head chamber 26, a pivoted damper plate 90 regulatesthe passage area between the suction leg 31 and chamber 26. A similarlylocated pivoted damper plate 91 is provided in the tail chamber 27 toregulate the flow area between tail suction leg 85 and chamber 27 andmanual adjusting control means for the damper plates 90 and 91 areprovided externally of the machine as shown at 92 and 93, respectively,in FIG. 1.

Air passing into the blower inlets 22 and 23 from the head and tailchambers goes -by way of fan or blower inlet chambers designated 95 and96, respectively, which communicate attheir upper ends with the head andtail chambers, such communication being under the control of slidedampers 98 and 99, respectively, which are regulated vertically by screwmechanism designated 100 and 101, respectively.

It is desired that air entering the head and tail chambers flowdownwardly (thence upwardly to the blowerinlet chambers, to furtherpromote precipitation of solid matter entrained in the air. Accordinglythe head and tail chambers are provided with fixed baffles designated102 and 103, respectively, which extend downwardly from the upper endsof these chambers medially between their entry and discharge sides.

It will be noted that airpasses upwardly through the scalper screen 80to suction leg 31 to entrain chaff, dust and other light impurities fromthe grain as it enters the screen structure. Again at the discharge end,the screened grain falls into the tail suction leg wherein air ispassing upwardly to the blower to entrain chaff and other relativelylight material which has not been previously separated or which wasremoved from the grain in the course of the cleaning and screeningprocess.

As shown in FIG. 1, the chaff hopper screw conveyors 88 and 89 areconnected for joint rotation by a belt 104, the conveyor screw 88 beingdrivenfrom the output shaft .63 of speed reducer 62 by a belt connection105.

The effective suction at the head and tail ends of the machine may beindependently regulated by means of a pair of sliding valve plates 107and 108 located against upper wall portions of the blower inlet chambers95 and 96, respectively. The valve plates 107 and 108 and the underlyingwall portions of the inlet chambers each have a multiplicity ofperforations, as indicated in FIG. 3, and the inlet chambers may thus beselectively vented to atmosphere in varying degrees by reason of thefact that the perforations of the valve plates are in registry with theunderlying perforations in the inlet chamber walls in greater or lessdegree, according to the horizontal positions of adjustment of the valveplates. The valve plates 107 and 108 may be entirely closed by movingthe plates so that the respective perforations ofthe plates and the wallportions are entirely out of registry.

Flow of good grain from screen 82 into tail leg 85 by way of a chute 110may be controlled or arrested as desired by vertical adjustment of asliding valve plate 109 associated with the tail leg 85.

Reference will now be had to further details of the construction andoperation of the screen deck structure illustrated particularly in FIGS.4 and 5. As indicated earlier herein, 'both the main screen 81 and thelowermost screen 82 comprise two screen sections lying in abuttingrelation, each section extending the full width of the screen deck. Themanner in which these screen sections are supported and retained in thescreen deck housing is shown in detail in FIG. 5, wherein the numeral120 designates an angle iron rail member fixed to the interior wall of aside wall '66 of the screen housing '65. It is to be understood that twopairs of rail members 120 are provided, an upper and a lower rail memberat the interior of each side wall 66 to provide ledges for supportingthe opposite side edges of the screens 81 and 82.

.The screen member 82 which is illustrated fragmentarily in FIG. 5includes a frame portion 121 of channel cross section which extendsthereabout and, is adapted to rest on the rail members at opposite sidesof the screen housing. In the illustrated instance frame portion 121 istapered as shown to fit between wedge shaped longitudinal gasketmembers122 of rubber or the like whereby the screen members fit snugly betweenthe housing side walls 66. For conveniently and securely locking thescreen members 81 and 82 in assembled position and for releasing themwhen desired the following locking arrangement is provided.

A longitudinal locking or-clarnping bar 125 overlies each rail member120 and is provided with inwardly projecting yoke portions 126 at itsopposite ends which are pivoted to the upperendsof rock arms, the rockarms at the feed end being designated 127 in FIG. 1 and the rock arms atthe delivery end being designated 128 in FIGS. 1 and 5. The rock arms127 at the feed end of the screen housing arefixed to the inner ends ofrock shafts 130 which, are jointly oscillated to effect lockingmovements of the. screen members 81 and 82 in a manner which will now bedescribed.

' Exteriorly of the side walls 66 of the screen housing the rock shafts130 are connected for joint rocking movement by arms 131 and aconnecting link 132. As shown in 'FIG. 1, an operating screw 135 ismounted at the feed end of screen housing 65 as at 136 for free rotationbut in a manner to prevent axial movement. An operating handle 137 isprovided at the outer end of screw 135 and its inner end engages aninternally threaded ar-m (not shown) on a rock shaft 138. Rock shaft 138has operating connection with the rock shafts 130 at opposite sides ofthe screen housing 65 by means of rock arms 140 and 141 and a connectinglink 142. I

From the foregoing it will be seen that operation of screw 135 in onedirection or the other, by manipulation of handle 137 will rock theseveral arms 127 in opposite directions. Since each arm 127, itscompanion arm 128, and the connecting locking or clamping bar 125 form,in conjunction with the side wall 66 to which the arms 127 and 128 arepivoted, a parallelogram linkage, rocking movements of the arms 127 areautomatically duplicated in the several arms 128.

Thus all of the locking or clamping bars 125 are jointly raise-d andlowered in a parallel manner by manipulation of handle member 137 ofscrew 135. This operation either clamps the lower flanges of the severalscreen framing channels 122 to the supporting rail members 120 orreleases them. Raising movements of the locking bars 125 causes them toengage the upper interior portions of the screen framing channels 121 toraise the screen sections clear of the supporting-rail members 120 forready removal.

In graincleaners of the prior art it is customary to provide means forcontinuously brushing the under surfaces of the screens to maintaintheir effectiveness. The apparatus of the present invention providesnovel means for accomplishing this function in the form of fluidpressure actuated motor means which acts directly upon the brushsupporting structure to reciprocate the same without mechanicalconnection to or transmission from the screen housing structuregenerally.

This is of particular advantage because of the vibratory action of thescreen structure and the desirability of isolating the same from theremainder of the machine as far as is practically feasible. Inthearrangement of the apparatus of the present invention the supportingand driving means for the brush mechanism is mounted independently ofthe screen structure itself.

Referring particularly to FIGS. 4 and 5, a generally rectangular brushsupporting frame is designated by the numeral and a plurality oflongitudinal rows of brush members is designated 151. The lateralspacing of the rows of brush members is approximately equal to or 7slightly less than the degree of lateral reciprocation of the brushsupporting frame 150 so that the entire under surface of the screens iskept clear and it will be noted that the individual brush members ofeach row are spaced from each other a short distance whereby they cleara series of lateral reinforcing angle members 152 of the screen members81 and 8 2.

The supporting and reciprocating means for the brush supporting frame150 is illustrated in FIG. 4, to which reference will now be had. Asindicated above, the brush frame support is independent of the remainderof the screen structure, including the screen housing. A pair of tubularbrush frame support shafts 155 and 156 extend laterally through thescreen housing just below each of the screen members 81 and 82 and thetwo pairs of shafts 155 and 156 are fixed at their opposite ends to thegeneral framework 20 of the apparatus as indicated in FI 4 Fixed to theunderside of each brush frame 150 adjacent to its four corners arebearings 160, preferably of the lineal ball type, which mount the brushframe on the tubular shafts 155 and 156 for lateral sliding movement.Reciprocation of each brush frame 150 is effected by an air cylinder 161wihch is attached'at one end to the machine framework 20 as at 162 andhas a piston rod 164 which is attached at its outer end to the brushframe 150 as at 165. It will be seen from the foregoing that both thereciprocable mounting of each brush frame and its reciprocating meansare supported entirely independently of the screen housing generally.

Each cylinder 161 is double acting and is provided with conventionalconduit and passage means for supplying operating air pressurealternately to its opposite ends. The means for shifting the valvepositions at each end of the lateral movement of the brush frame willnow be described. A valve shifting rod 168 extends through the tubularbrush frame mounting shaft 156 and engages a shifting lever 169 of avalve shifting mechanism 170.

A pair of Valve shifting collars 171 and 172 are slidably mounted onshaft 156 at each side of the screen housing just inwardly of the sidewalls 66 there-of and studs 174 extend through the collars 171 and 172and into valve shifting rod 168 whereby the collars 171 and 172 and thevalve shifting rod 168 are fixed for joint axial movement. The studspass through longitudinal slots in shaft 156 to permit such movementindependently of shaft 156.

As a brush frame 150 reaches its limit of movement in either directionone of the bearings 160 there-of which slides on shaft 156 during suchmovement abuts an adjacent valve shifting c-oll'a-r 171 or 172, as thecase may be,

and thus moves valve shifting rod 168 to reverse the valve shiftingmechanism 170 and thus reverse the direction of piston rod 164 and brushframe 150.

In FIG. 1 the numeral 180 designates an air pressure storage tank whichmay :be employed to supply operating fluid pressure to the brushactuating cylinders 161, pressure thereafter being generated by an aircompressor 181 8 driven from shaft by a belt connection 182. If desired,side panel members may be attached to the exterior of framework 20 toenclose the working parts of the apparatus.

In FIGS. 4 and 5 the numeral 185 designates a series of angle memberswhich are secured to the upper surfaces of the frame portions 121 of thescreen members in obliquely disposed position, as shown in FIG. 4. Graintending to move downwardly along the screen frame portion is thusdeflected inwardly to the screen surface proper at various points alongthe side edges of the screen surfaces.

I claim:

1. In a grain cleaner, a supporting frame, a screen and means mountingthe same for vibratory movement relative to the frame, a :brush framedisposed beneath said screen having brush members engageable against theunder side of said screen, means mounting said brush frame for slidingmovement beneath and generally parallel to said screen, air pressureactuated piston and cylinder means connecting between said supportingframe and said brush frame for sliding the latter, and means arranged incontrolling relation to said air pressure means including an operatingmember mounted on said supporting frame movable in response toengagement with said mounting means, said air pressure actuated pistonand cylinder means being operable to reciprocate said brush frame inresponse to said latter movement.

2. In a grain cleaner, a supporting frame, a screen and means mountingthe same for vibratory movement relative to the frame, support meansfixed to said supporting frame, a brush frame disposed beneath saidscreen having brush members engageable against the under side of saidscreen, slide bearing means mounted on said support means and supportingsaid brush frame for independent sliding movement beneath and generallyparallel to said screen, air pressure actuated piston and cylinder meansconnecting between said supporting frame and said brush frame forsliding the latter, and means arranged in controlling relation to saidair pressure means includingan operating member mounted on said supportmeans movable in response to engagement with said slide bearing means,said air pressure actuated piston and cylinder means being operable toreciprocate said brush frame in response to said latter movement.

References Cited by the Examiner UNITED STATES PATENTS 209,165 10/1878Fender 209-388 X 525,301 8/1894 Whit-more 209-388 X 1,908,788 5/1933Pulliam 15-97 2,510,741 6/1950 Coon 209388 3,058,133 10/ 1962 Haverbeng15-2l HARRY B. THORNTON, Primary Examiner.

R. HALPER, Assistant Examiner.

1. IN A GRAIN CLEANER, A SUPPORTING FRAME, A SCREEN AND MEANS MOUNTINGTHE SAME FOR VIBRATORY MOVEMENT RELATIVE TO THE FRAME, A BRUSH FRAMEDISPOSED BENEATH SAID SCREEN HAVING BRUSH MEMBERS ENGAGEABLE AGAINST THEUNDER SIDE OF SAID SCREEN, MEANS MOUNTING SAID BRUSH FRAME FOR SLIDINGMOVEMENT BENEATH AND GENERALLY PARALLEL TO SAID SCREEN, AIR PRESSUREACTUATED PISTON AND CYLINDER MEANS CONNECTING BETWEEN SAID SUPPORTINGFRAME AND SAID BRUSH FRAME FOR SLIDING THE LATTER, AND MEANS ARRANGED INCONTROLLING RELATION TO SAID AIR PRESSURE MEANS INCLUDING AN OPERATINGMEMBER MOUNTED ON SAID SUPPORTING FRAME MOVABLE IN RESPONSE TOENGAGEMENT WITH SAID MOUNTING MEANS, SAID AIR PRESSURE ACTUATED PISTONAND CYLINDER MEANS BEING OPERABLE TO RECIPROCATE SAID BRUSH FRAME INRESPONSE TO SAID LATTER MOVEMENT.